Field of the Invention
The present invention relates to a method for producing a composition for forming an organic film to be used in fine processing in a process of manufacturing a semiconductor apparatus including a semiconductor device, etc., in particular, a composition for forming a resist under layer film to be used in the multilayer resist method.
Description of the Related Art
The lithography technology used in the manufacture process of a semiconductor apparatus has contributed to the formation of a fine circuit pattern by shortening wavelength of the light source and selecting an appropriate resist composition thereto, and taken the lead in high integration and high speed processing of the semiconductor apparatus.
In order to prevent a pattern collapse when a cutting-edge fine circuit pattern is formed, the aspect ratio of a finished pattern needs to be adjusted appropriately. Therefore, it is necessary to appropriately adjust the thickness of the photoresist film. Currently, in the ArF lithography applied to mass production process, a poly(meth)acrylic resin is used as the photoresist. However, the poly(meth)acrylic resin has a low etching selectivity to a substrate, so that the film thickness of the photoresist formed according to the above requirements decreases the accuracy of pattern transfer to the substrate.
One solution for the above-mentioned problems is a multilayer resist method. In this method, a resist under layer film (e.g., a silicon-containing resist under layer film) having etching selectivity different from that of a photoresist film, i.e., a resist upper layer film, and an organic under layer film are interposed between the resist upper layer film and a substrate to be processed, a pattern is then formed in the resist upper layer film, the pattern is transferred to the silicon-containing resist under layer film by dry etching using the upper layer resist pattern as an etching mask, the pattern is then transferred to the organic under layer film by using the silicon-containing resist under layer film as an etching mask, and further the pattern is transferred to the substrate to be processed by dry etching using the organic under layer film as an etching mask.
The organic under layer film used in the multilayer resist method generally contains metal impurities derived from the raw material. Since the pattern transfer by dry etching is repeated in the multilayer resist method, these metal impurities may serve as an etching mask depending on the dry etching conditions, thereby occasionally transferring an abnormal pattern to the substrate to be processed of the semiconductor apparatus. In other words, when the substrate is processed by dry etching using an organic under layer film containing metal impurities, e.g. silicon, as a mask, the silicon in the organic film serves as a dry etching mask, and thereby column-like defects, so-called “cone defect”, are transferred to the substrate. In this case, the semiconductor apparatus shows electrical abnormalities such as open abnormality, short-circuit abnormality, etc., in the circuit, which results in the reduction in yield. Currently, purification of the raw material is considered to be the most effective way to prevent it, and for example, Patent document 1 discloses a method of purifying a raw material polymer by bringing it into contact with an acidic aqueous solution. Conventionally, however, various compositions for forming a film used in the semiconductor apparatus manufacture process are put into a container made of glass and connected to the manufacturing apparatus in almost cases. A small amount of elution from the container made of glass increases silicon content in the composition, which may cause defects occurring after dry etching. Thus, the method as disclosed in Patent document 1 is unsatisfactory to remove the defects occurring after dry etching.